The packaging of products in cartons typically employs a packaging machine of the type where the carton is filled and the closure flaps folded over each other to close the carton. Typically the carton is conveyed through the packaging apparatus where two sides are folded inwardly to expose an upwardly facing surface of at least one flap. The partially closed carton is then passed under a glue nozzle to apply one or more strips of glue on the upwardly facing surfaces in the direction of travel of the carton. The remaining flaps are then folded over to close the carton.
In order to increase the strength of the closures, it is generally desirable to apply more than one bead of adhesive to the closure flaps. Generally, multiple glue heads are provided to apply the beads of glue in a series of beads. It has further been desirable to apply a bead of adhesive around most of the perimeter of the closure flaps to reduce leakage or sifting of the contents. This type of apparatus typically includes a pair of stationary glue heads disposed above the conveyor such that glue is applied on a carton traveling on the conveyor in parallel lines along the outer edges of the closure flaps in the direction of travel. The bead of glue applied along the edges of the closure flap transverse to the direction of travel has been applied by stopping the forward movement of the carton and applying a bead of glue from a glue head moving across the conveyor. This method of gluing has the disadvantage of requiring that the carton be stopped momentarily while the glue is applied thereby disrupting the flow of the cartons. Other methods of sealing and closing cartons have avoided the disruption of the flow of cartons by rotating the cartons 90.degree. and then passing the cartons under a second set of glue heads to apply a bead of glue along the previously unglued edges. The cartons may be rotated either manually or by automated rotating means. Such gluing apparatus requires complicated rotating devices and glue heads, and head positioning devices in order to properly glue the closure flaps on the carton. These devices for gluing and closing cartons are deficient in not providing a continuous process without reorienting the cartons on the conveyor.
Examples of the previous methods of efficiently closing and gluing cartons include U.S. Pat. No. 4,503,659. This apparatus includes means for closing a pair of leading flaps on the package and a pair of trailing flaps on a packaging machine. A plurality of stationary glue heads are positioned in line with the packaging machine. One glue head is positioned to face downwardly and downstream aimed at the leading end of the package while the other glue head is facing downwardly and upstream at the trailing flap of the package. The heads direct a vertical line of glue on the flaps such when the flaps are closed, the flaps are secured by the glue.
The above-noted carton forming apparatus does not apply a bead of glue on the transverse edges of flaps to effectively glue the carton flaps. There is still a need in the art for a continuous carton forming apparatus which is capable of applying a bead of glue around the periphery of the carton closure flap.
Another facet in providing closures for cartons is to produce easy opening, sift-proof seals. Sift-proof seals are necessary when powders such as detergents are to be packaged. It has been found that this can be conveniently formed using a film closure where the film is heat-bonded to the carton, leaving tabs on each corner that can be used for removing this film seal in a peeling motion.